使用C＃从数据库获取数据

Question

iam looking to get the data from database .when i give the filename i want the pageinfo

   public string GetPageInfo(string filenames)
    {
        SqlConnection con = new SqlConnection("Data Source=.;Initial Catalog=;Integrated Security=True");

        con.Open();

        SqlCommand command = new SqlCommand("Select pageinfo from T_Pages where @pagename=filenames", con);

        command.Parameters.AddWithValue("@pagename", "filenames");
        // int result = command.ExecuteNonQuery();
        using (SqlDataReader reader = command.ExecuteReader())
        {
            if (reader.Read())
            {
                Console.WriteLine(String.Format("{0}", reader["pageinfo"]));
            }
        }

        con.Close();

    }

Answer 1

public string GetPageInfo(string filenames)

your method asks for a string to be returned at the end of the blocks.

according to your method's flow, the last thing it has to do is to write the result/s in the Console Window

if (reader.Read()) { Console.WriteLine(String.Format("{0}", reader["pageinfo"])); }

you have to choices:

1. either change public string GetPageInfo(string filenames) to public void GetPageInfo(string filenames) ; or,

2. return whatever column it is that you need from the database. that is changing:

if (reader.Read()) { Console.WriteLine(String.Format("{0}", reader["pageinfo"])); }

to

return reader["pageinfo"];

Answer 2

    int businessEntityID = 1;
string firstName = "Sander";
string middleName = null;
string lastName = "Rossel";
using (SqlConnection connection = new SqlConnection("Data Source=(local);Initial Catalog=AdventureWorks2014;Integrated Security=SSPI"))
using (SqlCommand cmd = new SqlCommand("UPDATE Person.Person SET FirstName = @FirstName, MiddleName = @MiddleName, LastName = @LastName WHERE BusinessEntityID = @BusinessEntityID", connection))
{
    cmd.Parameters.AddWithValue("FirstName", firstName);
    if (middleName == null)
    {
        cmd.Parameters.AddWithValue("MiddleName", DBNull.Value);
    }
    else
    {
        cmd.Parameters.AddWithValue("MiddleName", middleName);
    }
    cmd.Parameters.AddWithValue("LastName", lastName);
    cmd.Parameters.AddWithValue("BusinessEntityID", businessEntityID);
    connection.Open();
    cmd.ExecuteNonQuery();
}

i hope it's help you.